This invention relates to a process for producing spherical glass particles and to the spherical glass particles thus produced.
Glass spheres of relatively small particle size have found use in a wide range of applications such as in electronics and injection molding of plastics.
U.S. Pat. No. 4,390,368 discloses a free flowing plasma spray powder of substantially spherical particles having a composition consisting essentially of rhenium and tungsten. However, spherical glass particles are more difficult to form because of the higher viscosity of glass at its melting point. Therefore there is a tendency to form glass filaments as opposed to spheres.
U.S. Pat. No. 3,313,608 describes a method for producing spherical glass beads in which electrical and magnetic fields are used to break up a molten glass stream of about 0.15" in diameter. The beads are of relatively large particle size, with the size range being from about 0.005 to about 0.200 inches in diameter.
One prior art method for forming glass beads of relatively small size is by grinding the glass into small particles followed by injecting the particles into a frame from a burner to melt the particles and allow surface tension to form the particles into spheres. One disadvantage of this method is the formation of a large number of glass filaments along with the spheres. In order to be recycled in the operation, the filaments must be re-melted which is a costly operation.
Commercial glass beads have a particle size in the range of 10 micrometers to 53 micrometers with an average diameter of 30 micrometers. Such beads are described in an article entitled "Shear Band Formation in Polycarbonate-Glass Bead Composites," by M. E. J. Decker and D. Heikens, Journal of Materials Science 19 (1984) 3271-3275.
Therefore, glass spheres produced without production of undesirable filaments would be an advancement in the art and additionally a process for producing such spheres would be desirable.
U.S. Pat. Nos. 4,076,640, 4,191,556, 4,376,740, 4,490,601, 3,829,538, 4,252,599, 4,474,604, 4,435,342, 3,742,585, 4,332,617, 4,386,896, 4,264,641, 4,215,084, 4,069,045, 4,259,270, 3,907,546, 4,028,095, and 3,909,241, and Canadian Patent No. 941,690 relate to metal, alloy, or ore powders or particles or melts and are different from the present invention in that the present invention relates to spherical glass partricles.